The invention concerns a retractor with a rail from which a first holding arm protrudes at an angle and with a second holding arm which extends approximately parallel to the first holding arm and the distance from which is modifiable, and with functional elements mounted on the holding arms, of which at least one functional element has a section that extends transversely to a holding arm and which can be pivoted around a pin roughly parallel to one holding arm.
A retractor of this kind is, for example, known from document U.S. Pat. No. 5,025,779 or from U.S. Pat. No. 6,478,734 B1.
Retractors of this kind are for example used as rib retractors in open-heart surgery. The specialist terms thoracic and sternal retractors have become established here.
When a retractor is used on the sternum, the sternum (breastbone) is divided longitudinally and the functional elements attached to each of the holding arms are inserted into the opening in the sternum. Activating the drive mechanism moves the two holding arms apart and the thorax is opened up, enabling the surgeon to perform surgery inside the chest cavity.
Sternal retractors are used mainly in surgeries in which coronary vessels are replaced by other vessels; these are known as bypass surgeries. The left internal thoracic artery is currently generally used for this purpose. Technically, this is usually referred to as the (left) internal mammary artery, or (L)IMA for short. For this reasons, retractors used for this type of operation are also called IMA or LIMA retractors.
A further refinement of this surgery method is known as the minimally invasive direct coronary artery bypass (MIDCAB) technique. It was developed in the context of minimally invasive surgery. Here, access to the heart is gained not by opening the breastbone but via one of the intercostal spaces. The instruments developed for this purpose are known technically as MIDCAB retractors or sometimes also as lateral retractors.
It has proved useful for both techniques if the retractors used not only pull the two sides of the thorax opening apart but also raise the half of the thorax on the heart side in relation to the other one, since this gives better access to the heart.
U.S. Pat. No. 5,025,779 describes a rib retractor for raising one side of the thorax opening in relation to the other. The device described in the document has at least one functional element which is pivotable around a pin parallel to a holding arm, and the swivel position of which in relation to the retractor rail can be altered by means of an adjusting device.
This adjusting device is an adjusting screw. It passes through a swivel bracket by means of which the functional element is fixed to the holding arm, and rests against the section of the functional element which is at right angles to the holding arm. Turning the adjusting screw alters the distance between the swivel bracket and the functional element at the level of the adjusting screw. The fact that the swivel bracket and the functional element are connected such that they can pivot at a second place produces the desired change in the swivel position.
Use of a positioning device of this kind does have its disadvantages, however. One disadvantage of such a design is that the surgeon cannot feel exactly how much force is being applied to the patient's body, since the change in the swivel position is, as described above, made by turning an adjusting screw.
The amount of force applied to the patient's body acts along the axis of the positioning device. The force is absorbed partly by the positioning device and partly by the connection between the swivel bracket and the functional element. The only feeling which the surgeon has of the force applied is the degree of resistance encountered by the adjusting screw. The application of too much force may lead to trauma in the operating site.
A positioning device of this kind also places a relatively high focal stress on the functional element. Retraction of the thorax requires a high level of force, because the thorax is made up of numerous bones, muscles and tendons.
This high level of force thus acts directly on the relatively small bearing surface of the adjusting device.
Also, raising one half of the chest by means of an adjusting screw is time-consuming. To guarantee both sufficient accuracy of adjustment and an easy passage for the adjusting screw, adjusting screws with a narrow thread and small pitch are used. This means that the change in the swivel position per turn of the screw is small, thus necessitating prolonged screwing when there is a large change in the swivel position.
U.S. Pat. No. 6,159,231 describes a retractor in which the rail on which the two holding arms are mounted is angled. Here, raising the retractor is done using another external mechanism, such as a cable device.
This device does however have the disadvantage that it markedly reduces the surgeon's access to the operating site. With this design, the operating site can be accessed only from the side away from the lifting mechanism. Also, the device described in the patent is not symmetrical, and can therefore be used only for one side of the chest, generally the left one.
DE-C-198 57 320 describes a rib retractor in which the rail on which the two holding arms are mounted is in the shape of a convex arch. The retractor described has no other elements for raising one side of the operating window in relation to the other. This means that the difference in height between the two sides of the operating window is directly dependent on the width of the opening. This is determined solely by the fixed curvature of the arch-shaped rail. This means that the retractor cannot be adjusted to accommodate the circumstances of a particular operation.
U.S. Pat. No. 6,416,468 describes a lateral rib retractor which has a foot attached to one of the two holding arms. The device described in this patent is mechanically complicated and consists of a large number of individual parts, which makes it costly to manufacture and complicated to clean and sterilize. Also, the use of a separate foot can resulting in the foot slipping off and disrupting the operation.
U.S. Pat. No. 6,478,734 B1 describes as a fifteenth embodiment a retractor having a blade arm which is rotatably coupled via a cylindrical shaft to a drive block. The axis of the shafts extends into a longitudinal extension of the drive block. The blade arm is connected to a pad arm provided with a ratchet mechanism for turning blade arm via pad arm about the cylindrical shaft and locking said blade arm in different turning positions. This bulky blade arm/pad arm construction does not enable a surgeon to directly lift the chest but only via a lever. The lever geometry of blade arm/pad arm allows a simultaneous spreading and lifting movement only.
It is therefore the object of the invention to create a retractor for raising the ribs whereby the raising of one half of the chest is atraumatic and can be performed manually by the surgeon who can feel what he is doing.